Highly wear resistant composite rotary seals with wear layer at inner diameter and/or outer diameter embedded inside or between rubber layers

ABSTRACT

A composite journal seal for use in a roller cone drill bit may include a substantially ring shaped elastomeric body having at least two axial, radial, or canted sealing surfaces, at least one of the at least two axial, radial, or canted sealing surface being a dynamic sealing surface, and at least one reinforcement layer embedded at least 0.005 inches from the at least one dynamic sealing surface.

BACKGROUND

Drill bits are commonly used in, for example, the oil and gasexploration industry for drilling wells in earth formations. One type ofdrill bit commonly used in the industry is the roller cone drill bit.Roller cone drill bits generally comprise a bit body connected to adrill string or bottom hole assembly (BHA). Roller cone drill bitstypically include a plurality of roller cones rotatably attached to thebit body. The roller cones are generally mounted on steel journalsintegral with the bit body at its lower end. The roller cones furthercomprise a plurality of cutting elements disposed on each of theplurality of roller cones. The cutting elements may comprise, forexample, inserts (formed from, for example, polycrystalline diamond,boron nitride, and the like) and/or milled steel teeth that are coatedwith appropriate hardfacing materials.

When drilling an earth formation, the roller cone drill bit is rotatedin a wellbore, and each roller cone contacts the bottom of the wellborebeing drilled and subsequently rotates with respect to the drill bitbody. Drilling generally continues until, for example, a bit change isrequired because of a change in formation type is encountered in thewellbore or because the drill bit is worn and/or damaged. Hightemperatures, high pressures, tough, abrasive formations, and otherfactors all contribute to drill bit wear and failure.

When a drill bit wears out or fails as the wellbore is being drilled, itis necessary to remove the BHA from the well so that the drill bit maybe replaced. The amount of time required to make a bit replacement tripproduces downtime in drilling operations. The amount of downtime may besignificant, for example, when tripping in and out of relatively deepwells. Downtime can add to the cost of completing a well and is aparticular problem in offshore operations where costs are significantlyhigher. It is therefore desirable to maximize the service life of adrill bit in order to avoid rig downtime.

One reason for the failure of a roller cone drill bit is the wear thatoccurs on the journal bearings that support the roller cones. Thejournal bearings may be friction-type or roller-type bearings, and thejournal bearings are subjected to high loads, high pressures, hightemperatures, and exposure to abrasive particles originating from theformation being drilled. The journal bearings are typically lubricatedwith grease adapted to withstand tough drilling environments, and suchlubricants are an important element in the life of a drill bit.

Lubricants are retained within the journal bearing surface area by ajournal bearing seal, which is typically an O-ring type seal. The sealis typically located in a seal groove formed on an interior surface of aroller cone. The seal generally includes a static seal surface adaptedto form a static seal with the interior surface of the roller cone and adynamic seal surface adapted to form a dynamic seal with the journalupon which the roller cone is rotatably mounted. The seal must endure arange of temperature and pressure conditions during the operation of thedrill bit to prevent lubricants from escaping and/or contaminants fromentering the journal bearing. Elastomer seals known in the art areconventionally formed from a single type of rubber or elastomericmaterial, and are generally formed having identically configured dynamicand static seal surfaces with a generally regular cross section, but arealso known to be formed of composite materials so that dynamic and/orstatic sealing surface is formed from a different material from the restof the seal.

While journal seals formed from such rubber or elastomeric materialsdisplay excellent sealing properties of elasticity and conformity tomating surfaces, they display poor tribiological properties, low wearresistance, a high coefficient of friction, and a low degree ofhigh-temperature endurance and stability during operating conditions.Accordingly, the service life of bits equipped with such seals isdefined by the limited ability of the elastomeric seal material towithstand the different temperature and pressure conditions at eachdynamic and static seal surface.

Example O-ring seals known in the art that have been constructed in anattempt to improve O-ring seal service life include a multiple hardnessO-ring comprising a seal body formed from nitrile rubber, and a hardenedexterior skin surrounding the body that is formed by surface curing theexterior surface of the nitrile rubber. Although the patent teaches thatthe O-ring seal constructed in this manner displays improved hardnessand abrasion resistance, the act of hardening the entire outside surfaceof the seal body causes the seal to loose compressibility and otherrelated properties that are important to the seal's performance at thestatic seal surface.

Another example O-ring seal is a drill bit seal having a dynamic andstatic seal surface formed from different materials. The dynamic sealsurface is formed from a relatively low friction material comprising atemporary coating of Teflon that is deposited onto an inside diametersurface of the seal. The static seal surface is formed from the samematerial that is used to form the seal body. The Teflon surface acts toimprove the wear resistance of the seal at the dynamic seal surface.However, the use of Teflon on the dynamic seal surface only provides atemporary improvement in the coefficient of friction and easily wearsaway due to its low wear resistance.

A still other example O-ring seal is one comprising a dynamic sealsurface, formed from a single type of elastomeric material, and that hasa static seal surface that is formed from an elastomeric materialdifferent than that used to form the dynamic seal surface. Theelastomeric materials used to form the static seal surface is less wearresistant than the elastomeric material used to form the dynamic sealsurface, and the elastomeric materials forming the dynamic and staticseal surfaces are bonded together by chemically cross-linking to formthe seal body. Although such seal construction provides an improved wearresistance at the dynamic seal surface, when compared tosingle-elastomer seals, the amount of wear resistance that is providedis still limited to the ability of an elastomeric material. In such sealconstruction, the elastomeric materials used to form the static anddynamic seal surfaces, while being somewhat tailored to provide improvedservice at each such surface, must still remain chemically compatiblewith one another to permit the two to be chemically bonded together.Accordingly, while this type of seal construction provides a dynamicseal surface having improved wear resistance, when compared to asingle-elastomer seal, the dynamic seal surface will still be the pointof failure of the seal.

Accordingly, there exists a continuing need for developments in journalseal constructions that possess improved tribiological properties,improved wear resistance, a reduced coefficient of friction, and/orimproved high-temperature endurance and stability when compared toconventional journal seals.

SUMMARY

In one aspect, embodiments disclosed herein relate to a compositejournal seal for use in a roller cone drill bit that includes asubstantially ring shaped elastomeric body having at least two axial,radial, or canted sealing surfaces, at least one of the at least twoaxial, radial, or canted sealing surface being a dynamic sealingsurface, and at least one reinforcement layer embedded at least 0.005inches from the at least one dynamic sealing surface.

In another aspect, embodiments disclosed herein relate to a roller conedrill bit that includes a bit body; at least one journal extending froma lower portion of the bit body; a roller cone rotatably mounted on thejournal; and an annular seal positioned between the cone and thejournal, the annular seal comprising an elastomeric seal body having: afirst sealing surface for providing a seal along a dynamic rotarysurface formed between the seal body and one of the cone or the journal;a second sealing surface for providing a seal between the seal body andthe other of the cone or journal; and a reinforcement layer embedded atleast 0.005 inches from first sealing surface or the second sealingsurface.

In yet another aspect, embodiments disclosed herein relate to a rollercone drill bit that includes a bit body; at least one journal extendingfrom a lower portion of the bit body; a roller cone rotatably mounted onthe journal; and an annular seal positioned between the cone and thejournal, the annular seal comprising an elastomeric seal body having: afirst sealing surface for providing a seal along a dynamic rotarysurface formed between the seal body and one of the cone or the journal;a second sealing surface for providing a seal between the seal body andthe other of the cone or journal; and a reinforcement layer embeddedwithin the annular seal along at least 40% of the circumference of thefirst sealing surface.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is perspective view of roller cone drill bit.

FIG. 2 is a partial cross-sectional view of a roller cone drill bit.

FIGS. 3A and 3B show longitudinal and axial cross-sectional views of oneembodiment of a composite seal of the present disclosure.

FIGS. 4A and 4B show longitudinal and axial cross-sectional views of oneembodiment of a composite seal of the present disclosure.

FIGS. 5A and 5B show longitudinal cross-sectional views of twoembodiments of a composite seal of the present disclosure.

FIG. 6 shows a longitudinal cross-sectional view of one embodiment of acomposite seal of the present disclosure.

FIGS. 7A and 7B show longitudinal cross-sectional views of twoembodiments of a composite seal of the present disclosure.

FIG. 8A shows an axial cross-sectional view of a roller cone assembledon a drill bit journal with a prior seal.

FIG. 8B shows an axial cross-sectional view of a roller cone assembledon a drill bit journal with a composite seal according to the presentdisclosure.

FIG. 9 shows an axial cross-sectional view of one embodiment of acomposite seal of the present disclosure.

FIG. 10 shows a longitudinal cross-sectional view of one embodiment of acomposite seal of the present disclosure.

FIG. 11 shows a longitudinal cross-sectional view of one embodiment of acomposite seal of the present disclosure.

FIG. 12 shows a longitudinal cross-sectional view of one embodiment of acomposite seal of the present disclosure.

FIG. 13 shows a cross-sectional view of a composite seal of the presentdisclosure.

FIG. 14 shows a cross-sectional view of a composite seal of the presentdisclosure.

FIG. 15 shows a cross-sectional view of a composite seal of the presentdisclosure.

DETAILED DESCRIPTION

In one aspect, embodiments disclosed herein relate to seals used indrilling oil wells and the like. More particularly, embodimentsdisclosed herein relate to seals used in drill bits that are constructedfrom composite materials having a wear layer embedded inside or betweenelastomeric layers along at least a portion of at least one sealingsurface.

FIG. 1 shows a drill bit 8 comprising a bit body 9 and three rollercones 11 rotatably attached to the bit body 9. A means for attaching thedrill bit 8 to a bottom hole assembly (BHA) (not shown), such as athreaded connection 12, is positioned at an upper end of the bit body 9.A plurality of cutting elements 13 are disposed on the roller cones 11,which may be inserts inserted into holes in the roller cones or milledteeth that are integrally formed with the cone. Nozzles 15 are disposedin the bit body 9 so as to transmit a flow of drilling fluid from aninterior of the drill bit 8 to a wellbore (not shown) and to a spaceproximate the roller cones 11. The flow of drilling fluid serves to coolthe drill bit 8 (e.g., to cool the plurality of cutting elements 13) andto transport formation cuttings from the bottom of the wellbore to awellbore annulus (not shown) and, subsequently, to the surface.

FIG. 2 shows a cross sectional view of one leg 10 of the drill bit 8shown in FIG. 1. The drill bit 8 further comprises a rotational axis 14and three legs 10 (one of which is shown in FIG. 2) to which the rollercones 11 are rotatably attached. Each leg 10 includes a journal pin 16that extends downwardly and radially inwardly. However, it is alsowithin the scope of the present disclosure that the seals of the presentdisclosure may be used on journals that extend radially outward from thebit centerline, as described in US Patent Pub. No. 2011/0024197, whichis assigned to the present assignee and herein incorporated by referencein its entirety. A plurality of radial bearings and axial thrustbearings are disposed between the journal pin 16 and the roller cone 11.The plurality of radial and thrust bearings absorb and transfer loadsproduced by the roller cones 11 contacting a formation (not shown) anddrilling the wellbore. Effectively, loads are transferred from theroller cones 11 to the bit body 9 and, subsequently, to the BHA.

The plurality of radial and thrust bearings include, for example, radialbearing inserts 17, 19. These and other bearing surfaces are lubricatedby, for example, high-temperature grease. Grease may be pumped into theinterior of the journal pin 16/roller cone 11 interface through, forexample, a grease fill passage. Details of the grease fill passage andsystem, as well as a typical grease system pressure compensationmechanism may be found, for example, in U.S. Pat. No. 6,170,830 assignedto the present assignee and herein incorporated by reference in itsentirety. The lubricating grease reduces the friction and, as a result,the operating temperature of the bearings in the drill bit 8. Reducedfriction increases drill bit performance and longevity, among otherdesirable properties. The grease is retained in the load bearing regionsof the drill bit 8 by, for example, a seal 20. The seal 20 is typicallydisposed in a seal groove 22 formed on an internal surface of the rollercone 11. However, the seal groove 22 may alternatively be formed on anexternal surface of the journal pin 16, and the placement of the sealgroove 22 is not intended to be limiting. The seal 20 is typicallycompressed laterally by a selected amount in the seal groove 22. Thecompression, which is also referred to as “squeeze,” is produced whenthe seal 20 is compressed between the surface of the journal pin 16 andan inner surface 21 of the seal groove 22. The selected amount ofcompression may be varied, for example, by controlling either a radialthickness of the seal 22 of by controlling the depth of the seal groove22.

The seal 20 is adapted to retain lubricating grease proximate thebearings surfaces of the drill bit 8 and to serve as a barrier toprevent, for example, drilling fluid, hydrocarbons, and/or drillingdebris from impinging upon the interior of the journal pin 16/rollercone 11 interface and thereby damaging the radial and thrust bearings.Because of the variety of chemicals, hydrocarbons, and operatingconditions experienced when drilling the wellbore, the seal 20 isgeometrically designed and formed from selected materials to provide aneffective barrier between the bearings surfaces and the wellboreenvironment.

Referring now to FIGS. 3A and 3B, a seal 30 according to the presentdisclosure is shown. Seal 30 includes a seal body 32 that is formed inthe shape of a substantially flat ring and has seal surfaces on theinternal and external diameters 34, 36 thereof. At the ID surface 34, areinforcement layer 38 is embedded within seal 30 at least a selecteddistance from the ID surface. Reinforcement layer 38 may be provided tohelp improve the wear resistance of inner sealing surface 34 as adynamic sealing surface. While some prior bits may have included areinforcement layer bonded on the sealing surface, instead of embeddedwithin the seal a selected distance from the sealing surface, to improvethe wear resistance of the seals, these layers may be included with somedrawbacks, such as difficulty to control fabric alignment, the roughnessof the fabric layer can be abrasive to the surface with which the sealinterfaces and may also lead to grease leakage, and/or fabric frayingafter use. In contrast, the present reinforcement layer may provide thesame reinforcing or wear resistance effect to the seal, whilesimultaneously improving the sealing of the surface without risk ofabrasion or fraying and manufacturability.

Referring now to FIGS. 4A and 4B, a reinforcement layer 48 may beembedded in the seal or seal body a selected distance from both thesealing surface at the inner diameter 44 and the sealing surface at theouter diameter 46, which may be particularly desirable for a dualdynamic seal 40.

While the seals of FIGS. 3A-B and 4A-B, are shown as being compositeseals formed from two materials, the materials forming the seal body 32,42 and reinforcement layers 38, 48, the present disclosure is not solimited. For example, as shown in FIG. 5A, the composite seal 50 mayinclude a composite wear layer 55 (forming either the ID or OD) at asealing surface adjacent a rubber energizer seal body 52. In theembodiment shown in FIG. 5A, seal 50 includes a composite wear layer 55at the inner sealing surface 54, and (non-composite) wear layer 57 atthe outer sealing surface 56. Composite wear layer 55 is formed fromelastomeric material 55 a and a reinforcement layer 58, whereas wearlayer 57 is only formed from elastomeric material 57 a. Reinforcementlayer 58 is embedded a selected distance from the sealing surface 54within the elastomeric material 55 a. In the embodiment shown in FIG.5A, elastomeric material 55 a is distinct from energizer seal body 52but is the same material as elastomeric material 57 a. However, in otherembodiments, elastomeric materials 55 a and 57 a may be distinctmaterials. Further, as shown in FIG. 5B, composite seal 50 may includetwo composite wear layers 55 forming both the ID sealing surface 54 andOD sealing surface 56. Further, while the composite wear layers 55 and57 are shown as including an elastomeric material 55 a on both in theinner and outer sides of reinforcement material, it is within the scopeof the present disclosure, for example, that the composite wear layermay only be present on the exterior extent of the reinforcement layer,i.e., there is no elastomeric material 55 a between reinforcement layer58 and seal energizer seal body 52. Further, while the reinforcementlayer 38, 48 in FIGS. 3 and 4 has a substantially uniform thickness, theembodiments shown in FIGS. 5A and 5B possess a non-uniform thickness,being radially thicker at an axial cross-sectional plane than regionsaxially above and below. It is also envisioned that a reinforcementlayer with a substantially uniform thickness may be used in a compositewear layer, and a non-uniform thickness may be used in a seal without acomposite wear layer. Similarly, it is also envisioned that in sealswithout a composite wear layer, the reinforcement layer may also have asubstantially uniform thickness or a non-uniform thickness.

As mentioned in the description of all of the above figures, thereinforcement material layer is embedded within the seal, i.e., set backfrom the sealing surface a selected distance. As shown in FIG. 6, anexemplary composite seal of the present disclosure may have variousdimensions and/or relative dimensions involving the reinforcement layer68 and/or composite wear layer 65 a. For example, in variousembodiments, T_(y) may be more than about 0.005 inches, and ranging fromabout 0.010 to 0.050 inches in a particular embodiment, and at leastabout 0.020 inches in yet another particular embodiment. Further, T_(x)may be at least 0.01 inches in one embodiment, ranging from 0.010 inchesto 0.14 inches in another embodiment, and ranging from 0.015 to 0.08inches in yet another embodiment. For embodiments incorporating acomposite wear layer 65, the composite wear layer 65 extends a thicknessT_(i) that is at least 0.03 inches, at least 0.06 inches in anotherembodiment, ranging from 0.075 to 0.280 inches in another embodiment,and ranging from about 0.1 to 0.2 inches in yet another embodiment. Theratio of T_(i) to T_(o) (the total thickness of the seal) may be atleast 10 percent in one embodiment, at least 20 percent in anotherembodiment, up to 40 percent in another embodiment, up to 50 percent inyet another embodiment, and ranging from 30 to 50 percent in yet anotherembodiment. Further, it is also noted that the values of T_(x), T_(y),and T_(i) may be non-uniform along the circumference direction of a sealand/or having overlapping thicknesses depending on the arrangement ofthe layers.

The inventors of the present disclosure have found that by embedding thereinforcement layer under the sealing surface(s), instead of the layerforming or being exposed as the sealing, the sealing performance ofsealing surface may be significantly increased. The roughness andrigidity of the reinforcement layer forming the sealing surface(s) maylead to leakage of grease. The inventors also found that by addingreinforcement layer under the sealing surface(s), the amount ofdeformation in the seal at the dynamic sealing surface may be reduced ascompared to a conventional rubber seal. For example, referring to FIGS.7A and 7B, 7A shows a prior art seal 20 in a seal groove (not shown) ina roller cone 11 having sealing surfaces at its inner diameter 4 andouter diameter 6. In this embodiment, sealing surface at the innerdiameter 4 is a dynamic sealing surface as there is continual rotationalmotion between the seal 20 and the journal 16 on which the cone 11 isdisposed. As the roller cone 16 rotates, the inventors have found thatno reinforcement layer is included, there is an amount of deformation inthe seal surface, represented by the shift between A and A′. Incontrast, a seal according to the present disclosure, shown in FIG. 7Bmay have less shift between A and A′, i.e., seal deformation, for a seal70 present between journal 16 and roller cone 11 rotating around journal16 and having a reinforcement layer 78 embedded within the seal 70adjacent the inner sealing surface 74 and/or outer sealing surface 76.Less deformation in the seal may also result in better sealingproperties.

Referring now to FIGS. 8A and 8B, the composite seals 80 in theseembodiments include a substantially uniform reinforcement layer 88 incomposite wear layers 85; however, unlike the reinforcement layers 38,48 shown in FIGS. 3 and 4, the reinforcement layers 88 in FIGS. 8A and8B are embedded a selected distance or thickness from inner and outersealing surface 84, 86, the layers 88 extend in the axial direction tothe upper and lower surfaces 81, 83 and are exposed at such surfaces.Further, Applicants also note that the present disclosure does notexclude a composite seal that has some amount of exposure of thereinforcement layer at a sealing surface. Rather, in accordance withembodiments of the present disclosure, the reinforcement layer may beembedded under a sealing surface for at least 40% of the radialcircumference of the seal surface.

For example, referring now to FIG. 9, a composite seal 90 includesreinforcement layers 98 embedded under the inner and outer sealingsurfaces 94, 96 along a portion of the circumference of the twosurfaces. In one embodiment, this portion may comprise at least 40% ofthe radial circumference, at least 50% of the radial circumference inanother embodiment, and at least 60% in yet another embodiment. It iswithin the scope of the present disclosure that the circumferentialportion of the seal that does not have a reinforcement layer embeddedthe selected distance (described above) under the sealing surface mayhave no material along such circumferential portion, or may have thereinforcement layer at a greater or less distance than described aboveor exposed at the surface along such circumferential portion. Further,while the embodiment shown in FIG. 9 shows two reinforcement layers 98having substantially the same circumferential coverage of the inner andouter sealing surfaces 94, 96, it is within the scope of the presentdisclosure that either of such layers may be excluded, that either ofsuch layers may have lesser or greater or full coverage, that thecoverage may include differing circumferential portions of the sealingsurfaces, and/or that an overlapping of the layers may exist.

Further, while the previous embodiments illustrate the reinforcementlayer covering substantially the entire axial extent of the sealingsurface, the present invention is not so limited. For example, as shownin FIG. 10, a composite seal 1000 may include a reinforcement layer 1008that does not cover the entire axial extent of the sealing surfaces1004, 1006. In this embodiment, a reinforcement material is alsoembedded along at least a portion of the upper and/or lower surfaces(non-sealing or containment surfaces) 1001, 1003. While the embodimentin FIG. 10 illustrates a partial coverage, it is noted that if fullcircumferential and/or axial coverage is desired, the reinforcementlayer 1008 may take the general form of a torus reinforcement layer1108, embedded under the sealing surfaces and containment surfaces, asillustrated in FIG. 11. Further, depending on the particular coveragedesired, it may be necessary (or desirable from a manufacturingperspective) to have some overlap of the reinforcement layer 1208 withinthe seal 1200, as illustrated in FIG. 12. This overlap may be along acontainment or non-sealing surface (as shown in FIG. 12) or sealingsurface. Alternatively, there may be substantially full overlap in theform of a plurality of reinforcement layers 1208 embedded adjacent asealing surface. For example, in the case of a fabric reinforcementlayer, multiple pieces of fabric may be used atop each other to form aplurality of reinforcement layers or one piece of fabric may be foldedto create such multiple layers. In the case of fabric or other types ofreinforcement layers, it is within the scope of the present disclosurethat some amount of elastomeric material may separate the multiplelayers.

Further, while the above described embodiments generally describedcomposite seals 1300 as having sealing surfaces that are radial sealingsurfaces 1304, 1306, such as shown in FIG. 13, under which reinforcementlayer(s) 1308 are embedded, it is also within the scope of the presentdisclosure that a composite seal 1400 may have axial sealing surfaces1401 and 1403, under which reinforcement layer(s) 1408 may be embedded.Alternatively, the composite seal of the present disclosure may be acanted (or angled) seal 1500, as shown in FIG. 15, having a cantedsealing surface 1515, positioned intermediate axial surface 1501 andradial surface 1506, under which a reinforcement layer 1508 may beembedded. While the embodiment shown in FIG. 15 includes a cantedsealing surface 1515 positioned intermediate upper axial and outerradial directions, other canted seals may include a sealing surfaceunder which the reinforcement layer is embedded intermediate either ofthe upper or lower axial directions and either of the inner or outerradial directions.

Additionally, it is also noted that any of the embodiments illustratedmay include a composite wear layer having both a distinct elastomericmaterial from the remaining seal body and reinforcement layer or theseal may only include the reinforcement layer without multipleelastomeric materials.

Journal seals conventionally employed in roller cone bits are shaped inthe form of an O-ring and are formed from elastomeric or rubbermaterials, such as acrylonitrile polymers includingacrylonitrile-butadiene rubber (NBR), hydrogenated nitrile-butadienerubber (HNBR), carboxylated acrylonitrile butadiene, carboxylatedhydrogenated acrylonitrile butadiene, ethylene propylene, ethylenepropylene diene, fluoroelastomers including those available under thetrade names Viton and Kalrez manufactured by DuPont,tetrafluoroethylene-propylene copolymers (FEPM) available under thetrade name AFLAS® from Asahi Glass Co.), fluorocarbon (FKM) andperfluoroelastomer (FFKM), and the like. Other components sometimes usedin the polymers include activators or accelerators for the curing, suchas stearic acid, and agents that improve the heat resistance of thepolymer, such as zinc oxide and curing agents, or additives that affectthe material properties of the cured polymer, such as carbon nanotubes,carbon fibers, nano-sized polytetrafluoroethylene (PTFE), or silica- orsilicate-containing materials such as mica or diatomaceous earth.

The reinforcement layer(s) used in the present disclosure may includeharder elastomeric materials relative to the rubber matrix, nonelastomeric materials including plastic, fabric, and any othermaterials, including composite materials, that have a hardness highercompared to the seal matrix material and can be bonded to the rubbermatrix. One example nonelastomeric component is in the form of fiberssuch as those selected from the group consisting of polyester fiber,cotton fiber, stainless steel fibers aromatic polyamines (Aramids) suchas those available under the Kevlar family of compounds,polybenzimidazole (PBI) fiber, poly m-phenylene isophthalamide fibersuch as those available under the Nomex family of compounds, andmixtures or blends thereof such as PBI/Kevlar/stainless steel staplefabric. The fibers can either be used in their independent state and/orcombined with an elastomeric composite component, or may be combinedinto threads or woven into fabrics with or without an elastomericcomposite component.

Other composite materials suitable for use in forming composite sealsinclude those that display properties of high-temperature stability andendurance, wear resistance, and have a coefficient of friction similarto that of the polymeric material specifically mentioned above. Ifdesired, glass fiber can be used to strengthen the polymeric fiber, insuch case constituting the core for the polymeric fiber. An exemplarynonelastomeric polymeric material used for making the compositeconstruction is a polyester-cotton fabric having a density ofapproximately eight ounces per square yard. The polymeric material isprovided in the form of a fabric sheet having a desired mesh size.

In the embodiments where the composite seals of the present disclosureinclude a reinforcement material and a single elastomeric material, thereinforcement layer may be a fabric layer(s) or may have adurometer-hardness Shore A of at least 5 units greater than theelastomeric material, at least 10 greater in other embodiments, and atleast 20 greater in yet other embodiments.

In embodiments where the composite seal includes a composite wear layer,the seal may have a multi-piece construction comprising an elastomericenergizing seal body and the composite wear layer having a elastomericportion that is formed from a different material than the seal body andthat is selected to provide improved properties at a desired seallocation, e.g., to provide improved properties of wear resistance alonga sealing surface of the seal. The seal body and remaining seal portionare assembled together to form the multi-piece seal and do not requirechemical cross-linked bonding, but may include such crosslinked bondingif desired. It is understood, however, that multi-piece seals of thisinvention can be assembled together by adhesive, i.e., by means thatdoes not create chemical cross-linked bonding between the seal body andremaining sealing portion.

In such a particular embodiment, the seal body, for example, may beformed from an elastomer or rubber material that is capable of providingan energizing function to urge the dynamic seal surface against adynamic roller cone bit surface. Suitable elastomer and rubber materialsinclude those mentioned above and others such as those selected from thegroup of fluoroelastomers including those available under the tradenames Viton and Kalrez manufactured by DuPont, carboxylated elastomerssuch as carboxylated acrylonitrile butadiene, carboxylated hydrogenatedacrylonitrile butadiene, acrylonitrile-butadiene rubber (NBR),hydrogenated acrylonitrile-butadiene rubber (HNBR) and the like.Suitable elastomeric materials have a modulus of elasticity at 100percent elongation of from about 500 to 2,000 psi (3 to 12 megapascals),a minimum tensile strength of from about 2,000 to 7,000 psi (6 to 42megapascals), elongation of from 100 to 500 percent, die C tear strengthof at least 200 lb/in. (1.8 kilogram/millimeter), durometer hardnessShore A in the range of from about 60 to 95, and a compression set after70 hours at 100° C. of less than about 18 percent, and preferably lessthan about 16 percent. Particular elastomeric materials useful in thepresent disclosure include proprietary NBR compounds manufactured bySmith Bits and Smith Services, A Schlumberger Company, under the productnames HSN-8A, W-122, W-77, 401, and E-77. In a particular embodiment,where high temperature applications are intended, the seal body and/orcomposite layer may include one of FKM, FEPM, and FFKM.

The elastomeric material forming the composite wear layer may include adifferent elastomer than selected for the seal body, or may includeadditives selected to alter the material properties of the elastomericbody. For example, the elastomeric material of the wear layer may have adurometer hardness Shore A of at least 5 or at least 10 units greaterthan the elastomeric material of the seal body. Further, a reinforcementmaterial may have a durometer hardness Shore A of at least 5 or at least10 units greater than the elastomeric material of the wear layer inwhich it is embedded.

The seal construction may include one or more lubricant additives,disbursed uniformly through the elastomeric material, to further reducewear and friction along the surface of the seal. Suitable lubricantadditives include those selected from the group consisting ofpolytetrafluoroethylene (PTFE), hexagonal boron nitride (hBN), flakegraphite, molybdenum disulfide (MoS₂) and other commonly knownfluoropolymeric, dry or polymeric lubricants, and mixtures thereof. Thelubricant additive may be used to provide an added degree of lowfriction and wear resistance to the elastomeric component of thecomposite material that is placed in contact with a rotating surface. Aparticular lubricant additive is hBN manufactured by Advanced ceramicsidentified as Grade HCP, having an average particle size in the range offrom about five to ten micrometers. Multi-piece seals constructedaccording to principles of this disclosure may comprise up to about 20percent by volume lubricant additive.

The composite seals of the present disclosure may be formed from amulti-piece construction. Specifically, a seal body portion may beextruded as one piece, onto which a reinforcement layer may be placed atthe appropriate surface (depending on the type of sealing surface to bereinforced). A separate piece or separate pieces of elastomer may beextruded and placed atop the reinforcement layer. Alternatively,multiple coats of uncured liquid elastomeric material in a suitablesolvent may be applied to the reinforcement layer to form an elastomericcoating thickness so that the reinforcement material is sufficientlyembedded within the seal from the sealing surface. Further, in the caseof multiple layers of reinforcement layer being used, particularly inthe case of a fabric sheet being used, coatings of elastomeric materialdissolved in a solvent may be applied onto the fabric to saturate thefabric and also build up an amount of elastomeric material betweenmultiple sheets of fabric. All components are placed in a mold, the moldis heated and pressurized to simultaneously form the seal and cure orvulcanize (and optionally crosslink) the elastomer component(s) of thecomposite seal.

Embodiments of the present disclosure may provide at least one of thefollowing advantages. The presence of reinforcement layer(s) may resultin enhanced wear resistance of the sealing surfaces, and do so in amanner that results in better sealing characteristics. Further, theembedding of the reinforcement layer and multi-piece construction of thecomposite seal may result in easier manufacturing particularly becausethe sealing surface remains a uniform elastomeric material and with moreconsistent performance by reducing the amount of deformation in the sealsurface and the potential breakdown of the reinforcement layer, whichcan result in failure of the seal, the bit body surfaces and cause bitfailure.

Even further, the composite seals of the present disclosure may beparticularly suitable for high temperature applications. Specifically,when drilling into oil, gas, and geothermal reservoirs, hightemperatures often experienced in deep and/or geologically active areaswith hard lithologies (necessitating use of roller cone drill bits)place high demands on the seal (and thus bit) performance, specificallyresistance to thermal degradation to avoid bearing failure. Variousembodiments of the composite seals of the present disclosure may beparticularly suitable for such high temperature applications.

Although only a few example embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications are possible in the example embodiments without materiallydeparting from this invention. Accordingly, all such modifications areintended to be included within the scope of this disclosure as definedin the following claims. In the claims, means-plus-function clauses areintended to cover the structures described herein as performing therecited function and not only structural equivalents, but alsoequivalent structures. Thus, although a nail and a screw may not bestructural equivalents in that a nail employs a cylindrical surface tosecure wooden parts together, whereas a screw employs a helical surface,in the environment of fastening wooden parts, a nail and a screw may beequivalent structures. It is the express intention of the applicant notto invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of theclaims herein, except for those in which the claim expressly uses thewords ‘means for’ together with an associated function.

1. A composite journal seal for use in a roller cone drill bit, comprising: a substantially ring shaped elastomeric body having at least two axial, radial, or canted sealing surfaces, at least one of the at least two axial, radial, or canted sealing surface being a dynamic sealing surface, at least one reinforcement layer embedded at least 0.005 inches from the at least one dynamic sealing surface.
 2. The composite journal seal of claim 1, wherein the at least one reinforcement layer comprises a fabric sheet.
 3. The composite journal seal of claim 1, wherein the at least one dynamic sealing surface is formed from a composite wear layer comprising a second elastomeric material in which the reinforcement layer is embedded.
 4. The composite journal seal of claim 1, wherein the at least one reinforcement layer is embedded at least 0.010 inches from the at least one dynamic sealing surface.
 5. The composite journal seal of claim 1, wherein the at least one reinforcement layer extends circumferentially along at least 50% of the at least one dynamic sealing surface.
 6. A roller cone drill bit, comprising: a bit body; at least one journal extending from a lower portion of the bit body; a roller cone rotatably mounted on the journal; and an annular seal positioned between the cone and the journal, the annular seal comprising an elastomeric seal body having: a first sealing surface for providing a seal along a dynamic rotary surface formed between the seal body and one of the cone or the journal; a second sealing surface for providing a seal between the seal body and the other of the cone or journal; and a reinforcement layer embedded at least 0.005 inches from first sealing surface or the second sealing surface.
 7. The drill bit of claim 6, wherein the at least one reinforcement layer comprises a fabric sheet.
 8. The drill bit of claim 6, wherein the reinforcement layer is embedded at least 0.005 inches from the first sealing surface.
 9. The drill bit of claim 8, wherein the first sealing surface is formed from a composite wear layer comprising a second elastomeric material in which the reinforcement layer is embedded.
 10. The drill bit of claim 8, wherein the at least one reinforcement layer is embedded at least 0.010 inches from the first sealing surface.
 11. The drill bit of claim 9, wherein the at least one reinforcement layer is embedded at least 0.020 inches from the first sealing surface.
 12. The drill bit of claim 6, wherein the first sealing surface is a radial sealing surface along the inner diameter of the annular seal.
 13. The drill bit of claim 9, wherein the second elastomeric layer is at least 5 durometer-hardness Shore A greater than the elastomeric seal body.
 14. The drill bit of claim 9, wherein the wear layer extends up to 50 percent of the total cross-sectional thickness of the annular seal from the first sealing surface.
 15. The drill bit of claim 9, wherein a third elastomeric material forms the second sealing surface.
 16. The drill bit of claim 15, wherein the third elastomeric material has a reinforcement layer embedded therein.
 17. The drill bit of claim 6, wherein the reinforcement layer is embedded under at least a portion of a containment surface.
 18. The drill bit of claim 9, wherein the second elastomeric material comprises at least one of acrylonitrile butadiene, carboxylated acrylonitrile butadiene, hydrogenated acrylonitrile butadiene, carboxylated hydrogenated acrylonitrile butadiene, ethylene propylene, ethylene propylene diene, tetrafluoroethylene and propylene copolymer, fluorocarbon, or perfluoroelastomers, wherein the second elastomeric material is harder than the elastomeric seal body.
 19. The drill bit of claim 6, wherein the reinforcement material comprises at least one material harder and/or stronger than the elastomeric seal body selected from the group consisting of an elastomer, plastic, metal, and fabric.
 20. A roller cone drill bit, comprising: a bit body; at least one journal extending from a lower portion of the bit body; a roller cone rotatably mounted on the journal; and an annular seal positioned between the cone and the journal, the annular seal comprising an elastomeric seal body having: a first sealing surface for providing a seal along a dynamic rotary surface formed between the seal body and one of the cone or the journal; a second sealing surface for providing a seal between the seal body and the other of the cone or journal; and a reinforcement layer embedded within the annular seal along at least 40% of the circumference of the first sealing surface.
 21. The drill bit of claim 20, wherein the at least one reinforcement layer comprises a fabric sheet.
 22. The drill bit of claim 20, wherein the reinforcement layer is embedded at least 0.005 inches from the first sealing surface.
 23. The drill bit of claim 20, wherein the first sealing surface is formed from a composite wear layer comprising a second elastomeric material in which the reinforcement layer is embedded.
 24. The drill bit of claim 23, wherein the second elastomeric layer is at least 5 durometer-hardness Shore A greater than the elastomeric seal body.
 25. The drill bit of claim 23, wherein the wear layer extends up to 50 percent of the total cross-sectional thickness of the annular seal from the first sealing surface. 